Small tool grinding of the large aperture segment mirror based on six axis robotic arm

The splicing sub mirrors of the Thirty Meter Telescope(TMT) primary mirror are off-axis aspheric shapes with large aspheric value. In order to reduce the time of stressed mirror annular polishing(SMAP), the mirror surface will be fine grinding using computer numerical control (CNC) processing device based on a six axis robotic arm before SMAP process, and the segment mirror will be lapping quickly benefit by high removal efficiency of fine grinding compared to polishing. In this article the principles of CNC processing, robotic arm motion controlling, and the experiment of fine grinding removal function are introduced. Finally, the segment mirror of TMT at the out edge is processed, and the fabrication convergence curve and final surface residual distribution are obtained. The optimized machining experience can further shorten the processing time and be used for early aspheric process of segments.